1. Field of the Invention
The present invention relates to an image forming apparatus.
2. Description of the Related Art
Conventionally, when a jam occurs at the fixing roller of a fixing unit in an image forming apparatus and no jam processing is performed, a recording medium may wind around the fixing roller in during a recovery or warm-up operation, thus causing a problem. Japanese Patent Laid-Open No. 7-140836 discloses a structure for preventing a recording medium from winding around the fixing roller, by arranging sensors upstream and downstream (recording medium feeding and discharge sides) of the fixing unit, detecting, using these sensors, a recording medium which remains in an area upstream or downstream from the fixing unit, and stopping a fixing roller driving motor.
Such a conventional technique which uses sensors arranged upstream and downstream from the fixing unit is effective in an image forming apparatus operating at medium to low speed (e.g., 10 to 60 sheets per minute) processing capability. However, in an image forming apparatus capable of high-speed processing of 80 or more sheets per minute, even if sensors are arranged upstream and downstream from the fixing roller, it takes a long time after a jam has been detected before the fixing roller drive motor stops. Accordingly, the recording medium cannot be stopped (cannot be detected) at the detection positions of the upstream and downstream sensors. In this case, if the sensors do not detect a recording medium remaining near the fixing roller, the control unit of the image forming apparatus erroneously determines on the basis of the detection results of the sensors that the image forming apparatus is in a normal state.
Furthermore, if the image forming apparatus is power-cycled while the sensors are not detecting any recording medium, the image forming apparatus will execute the warming-up operation and the like. Accordingly, an undetected recording medium remaining at the fixing roller will undesirably wind around the fixing roller.